1. Field of the Invention
The present invention relates to a mobile robot that moves while communicating by radio with a managing computer and a controller for the same.
2. Description of the Related Art
In recent years, a technique of issuing a task execution command signal to a mobile robot to have it execute a task has been proposed. Such a mobile robot cannot be remotely controlled by radio if the mobile robot has been moved outside the reaching range of radio waves, and a person needs to take the mobile robot back to within the reaching range of radio waves by hand.
As to this problem, in Japanese Patent Application Laid-Open Publication No. 2004-260769 (hereinafter called a reference 1), paragraphs 0008-0012 and FIGS. 4-6, a mobile robot has been proposed which is configured to move autonomously to a radio link-feasible point according to a radio wave intensity map created based on the radio wave intensities obtained while moving if having moved outside the reaching range of radio waves.
Further, in Japanese Patent Application Laid-Open Publication No. 2005-025516 (hereinafter called a reference 2), paragraph 0016 and FIG. 9, a mobile robot has been proposed wherein, where a plurality of the mobile robots are operating, for a mobile robot having moved into an area where radio waves are weak, another mobile robot relays communication with a base station.
However, because the mobile robot described in the reference 1 selects a movement path based on the radio wave intensity map, the mobile robot may not be able to return to a communication-feasible area if communication is cut off by a cause other than radio wave intensity such as noise.
As to the mobile robot described in the reference 2, where only one mobile robot is operating, the mobile robot cannot have communication with the base station relayed, and when having moved outside the reaching range of radio waves, the mobile robot may not be able to return to a communication-feasible area.
Of the above conventional art, in the technique of the reference 1, a movement path for restoration is selected based on only the radio wave intensity map. With this technique, there is the problem that, because radio communication can be cut off by a cause other than radio wave intensity such as noise, radio communication may not be restored depending on the radio environment even if the mobile robot has moved to a place where radio waves are enough in intensity.
With the technique of the reference 2, there is the problem that, where only one mobile robot is operating, radio communication cannot be restored if the mobile robot has moved outside the reaching range of radio waves.
Further, a mobile robot is known which transmits and receives information to and from a managing computer via a radio base station linked to the managing computer and which autonomously moves in a movement area (refer to, e.g., the references 1, 2).
The robot described in the reference 1 is a movable house-sitting monitoring robot having a radio device, a camera, and an infrared transmitter. This robot receives by the radio device instructions transmitted over a network by a user from a remote place, and in response to the instructions, moves in the home from which the user is absent, and operates electric appliances with the use of the infrared transmitter or monitors its surroundings with the use of the camera. Furthermore, if having moved to a point where the state of radio waves received by the radio device is bad, this robot will automatically return to a point where the radio wave state is good (a restoring process).
The robot described in the reference 2 is a humanoid bipedal walking robot having voice recognition and voice synthesis devices and can communicate well with a human who gives instructions to the robot by voice or is involved in the work of the robot. For example, the robot transmits a tag ID obtained from a human with a detection tag who is near the robot to a managing computer, receives personal information (such as name and job title) of the human from the managing computer, and thus can perform interaction tailored for the human.
However, with the conventional art, when the robot has moved to a point where the radio environment is bad, the following problems occur:
The robot described in the reference 1 is a house-sitting monitoring robot and not one intended to communicate with humans. If a human (user) near the robot observes the robot moving, he/she cannot determine whether the robot is moving toward a workplace to work or from a position where the radio wave state is bad to a position where good. Hence, when the user gives a new instruction to the robot that is moving, the new instruction will not reach the robot if the robot is moving for restoration. Thus, when giving a new instruction to the robot moving, the user cannot confirm whether the robot has correctly received the new instruction.
Another robot described in Japanese Patent Application Laid-Open Publication No. 2005-288573 (hereinafter called a reference 3), paragraphs 0147-0167 and FIG. 15 cannot correctly communicate data with a managing computer when having moved to a position where the radio environment is bad. For example, if the robot cannot receive personal information of a detected human from the managing computer, a failure occurs in communication with the detected human. In such a case, humans near the robot cannot determine whether the change in the robot's response is caused by a failure or degradation in the radio environment or whether it is intended in design. Thus, they cannot determine how to deal with it.
As such, there is the problem that the utility (variance of freedom) of the robot is reduced because the radio wave state cannot be recognized. In other words, restoration of the radio communication such as cut off cannot be provided. That is, there is the problem that a human has to analyze the cause to restore the robot, which makes the robot difficult to use.